Measurements Of Attenuation Coefficient Research Articles

Method for Estimating the Diffuse Attenuation Coefficient from the Beam Attenuation Coefficient in the Waters of the Black Sea

The vertical attenuation coefficient of downward irradiance is one of the hydro-optical characteristics that determine the parameters of the light field in the sea. Information from the vertical attenuation coefficient of downward irradiance (or the diffuse attenuation coefficient) is necessary when determining an important biological and ecological parameter of water basin — the thickness of the euphotic layer. A possible method for estimating the vertical attenuation coefficient of downward irradiance (or the diffuse attenuation coefficient) from measurements of the beam attenuation coefficient at a wavelength of 525 nm for the Black Sea waters is described. The Black Sea waters are characterized by an increased content of dissolved organic matter and belong to type II waters (according to the Morel classification). Examples of the application of the method are given, which showed a quite high correlation (R = 0.85) between the values of the vertical attenuation coefficient of downward irradiance determined from in situ measurements of underwater irradiance with a photometer and calculated from in situ measurements of the beam attenuation coefficient with a transparency meter. The standard deviation of the calculated values from the measured ones is 0.008 m–1, the maximum deviation is 0.023 m–1.

A framework to model charge sharing and pulse pileup for virtual imaging trials of photon-counting CT

Objective.This study describes the development, validation, and integration of a detector response model that accounts for the combined effects of x-ray crosstalk, charge sharing, and pulse pileup in photon-counting detectors.Approach.The x-ray photon transport was simulated using Geant4, followed by analytical charge sharing simulation in MATLAB. The analytical simulation models charge clouds with Gaussian-distributed charge densities, which are projected on a 3×3 pixel neighborhood of interaction location to compute detected counts. For pulse pileup, a prior analytical method for redistribution of energy-binned counts was implemented for delta pulses. The x-ray photon transport and charge sharing components were validated using experimental data acquired on the CdTe-based Pixirad-1/Pixie-III detector using monoenergetic beams at 26, 33, 37, and 50 keV. The pulse pileup implementation was verified with a comparable Monte Carlo simulation. The model output without pulse pileup was used to generate spatio-energetic response matrices for efficient simulation of scanner-specific photon-counting CT (PCCT) images with DukeSim, with pulse pileup modeled as a post-processing step on simulated projections. For analysis, images for the Gammex multi-energy phantom and the XCAT chest phantom were simulated at 120 kV, both with and without pulse pileup for a range of doses (27-1344 mAs). The XCAT images were evaluated qualitatively at 120 mAs, while images for the Gammex phantom were evaluated quantitatively for all doses using measurements of attenuation coefficients and Calcium concentrations.Main results.Reasonable agreement was observed between simulated and experimental spectra with Mean Absolute Percentage Error Values (MAPE) between 10%and 31%across all incident energies and detector modes. The increased pulse pileup from increased dose affected attenuation coefficients and calcium concentrations, with an effect on calcium quantification as high as MAPE of 28%.Significance.The presented approach demonstrates the viability of the model for enabling VITs to assess and optimize the clinical performance of PCCT.

Evaluation of fatigue damage of structural steel based on attenuation of laser-induced surface acoustic wave

ABSTRACT In this paper, the fatigue damage degree of low-alloy structural steel is evaluated by using the attenuation characteristics of laser-induced surface acoustic wave (SAW) during propagation. Taking the typical structural steel material Q345 as an example, a cracks model of fatigue damage is established, and the finite element method is used to solve the model. The results showed that the attenuation coefficient of SAW can reflect the depth and density of fatigue cracks. The surface measurement experiments of specimens with stress cycles of 0, 50000, 100000, 150000, and 200,000 showed that with the increase of stress cycles, the attenuation coefficient of SAW increases as a whole, indicating that it is feasible to evaluate the fatigue damage degree based on the attenuation of SAW. A method of applying tensile stress to the material to improve the sensitivity of fatigue damage evaluation is proposed. The tensile stress is used to offset the horizontal amplitude of the SAW, keeping the fatigue cracks in an open state and increasing the attenuation coefficient of SAW. The attenuation coefficient measurement experiment shows that this method is feasible.

Measurement of average mass attenuation coefficient of air for 137Cs gamma-ray irradiation beam

Abstract The average mass attenuation coefficient of air for the KRISS 137Cs gamma-ray irradiation beam was measured using a 30 cm-long vacuum-sealable cylindrical column. Six different models of ionization chambers were employed for the measurement. Under ambient room conditions, the average mass attenuation coefficient was found to be (0.0778 ± 0.0012) cm2 g−1 across the six chambers. This coefficient will be used to adjust the variation in air kerma with air density for the 137Cs gamma-ray irradiation beam.

Attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard as a potential phantom material using Monte Carlo GATE

This work aimed to determine the linear and mass attenuation coefficients of soy-lignin bonded Rhizophora spp. particleboard intended for use as a phantom material using Monte Carlo GATE simulation. At a desired density of 1.0 gcm-3, particleboard constructed of Rhizophora spp. wood trunk bonded with soy flour and lignin was created. The sample’s elemental composition was identified using energy dispersive X-ray spectroscopy. The GATE software was used to simulate the setup with the histories of 1 × 107, and comparison was made between the experimental and simulation data. The disparities between the linear and mass attenuation coefficients of the samples experimentally measured and calculated using GATE at low energy photons were quite small. The result revealed a good agreement between the experimental and simulation data, and the attenuation coefficients were in close proximity with XCOM of water. The outcome revealed GATE adequacy for validation of attenuation coefficient measurement in bioresources phantom material for medical physics application.

Feasibility of Monitoring Tissue Properties During Microcirculation Disorder Using a Compact Fiber-Based Probe With Sapphire Tip.

One of the urgent tasks of modern medicine is to detect microcirculation disorder during surgery to avoid possible consequences like tissue hypoxia, ischemia, and necrosis. To address this issue, in this article, we propose a compact probe with sapphire tip and optical sensing based on the principle of spatially resolved diffuse reflectance analysis. It allows for intraoperative measurement of tissue effective attenuation coefficient and its alteration during the changes of tissue condition, caused by microcirculation disorder. The results of experimental studies using (1) a tissue-mimicking phantom based on lipid emulsion and hemoglobin and (2) a model of hindlimb ischemia performed in a rat demonstrated the ability to detect rapid changes of tissue attenuation confirming the feasibility of the probe to sense the stressful exposure. Due to a compact design of the probe, it could be useful for rather wide surgical operations and diagnostic purposes as an auxiliary instrument.

Intersystem and Interoperator Agreement of US Attenuation Coefficient for Quantifying Liver Steatosis.

Background The extent of liver steatosis can be assessed using US attenuation coefficient (AC) algorithms currently implemented in several US systems. However, little is known about intersystem and interoperator variability in measurements. Purpose To assess intersystem and interoperator agreement in US AC measurements for fat quantification in individuals with varying degrees of liver steatosis and to assess the correlation of each manufacturer's AC algorithm results with MRI proton density fat fraction (PDFF). Materials and Methods This prospective study was conducted at Southwoods Imaging, Youngstown, Ohio, September 30-October 1, 2023. Two operators independently obtained AC measurements using eight US systems equipped with an AC algorithm from different manufacturers. On the same day, MRI PDFF measurement was performed by a different operator. Correlation between US AC and MRI PDFF was assessed using a mixed-effects model. Agreement between systems and operators was evaluated using the intraclass correlation coefficient (ICC). Results Twenty-six individuals (mean age, 55.4 years ± 10.7 [SD]; 16 female participants) were evaluated. The correlation of US AC with MRI PDFF was high for five AC algorithms (r range, 0.70-0.86), moderate for two (r = 0.62 for both), and poor for one (r = 0.47). In pairwise comparisons, none of the pairs of systems achieved excellent agreement (overall ICC = 0.33 [95% CI: 0.15, 0.52]). One pair showed good agreement (ICC = 0.79 [95% CI: 0.66, 0.87]), eight pairs showed moderate agreement (ICC range, 0.50 [95% CI: 0.22, 0.69] to 0.73 [95% CI: 0.49, 0.85]), and 19 pairs showed poor agreement (ICC range, 0.11 [95% CI: -0.06, 0.37] to 0.48 [95% CI: 0.20, 0.67]). Interoperator agreement on AC value was excellent for the Samsung Medison algorithm (ICC = 0.90 [95% CI: 0.80, 0.96]), good for the Siemens Healthineers (ICC = 0.76 [95% CI: 0.54, 0.89]) and Canon Medical Systems (ICC = 0.76 [95% CI: 0.16, 0.92]) algorithms, and moderate for the remaining algorithms (ICC range, 0.50 [95% CI: 0.16, 0.73] to 0.74 [95% CI: 0.51, 0.88]). The mean AC value obtained by the two operators did not differ for any system except the system from Canon Medical Systems. Conclusion There was substantial variability in AC values obtained with different US systems, precluding interchangeability between systems for liver steatosis diagnosis and follow-up imaging. Interoperator agreement ranged from moderate to excellent. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Han in this issue.

Assessing Quality of Ultrasound Attenuation Coefficient Results for Liver Fat Quantification.

Algorithms for quantifying liver fat content based on the ultrasound attenuation coefficient (AC) are currently available; however, little is known about whether their accuracy increases by applying quality criteria such as the interquartile range-to-median ratio (IQR/M) or whether the median or average AC value should be used. AC measurements were performed with the Aplio i800 ultrasound system using the attenuation imaging (ATI) algorithm (Canon Medical Systems, Otawara, Tochigi, Japan). Magnetic resonance imaging proton density fat fraction (MRI-PDFF) was the reference standard. The diagnostic performance of the AC median value of 5 measurements (AC-M) was compared to that of AC average value (AC-A) of 5 or 3 acquisitions and different levels of IQR/M for median values or standard deviation/average (SD/A) for average values were also analyzed. Concordance between AC-5M, AC-5A, and AC3A was evaluated with concordance correlation coefficient (CCC). A total of 182 individuals (94 females; mean age, 51.2y [SD: 15]) were evaluated. A total of 77 (42.3%) individuals had S0 steatosis (MRI-PDFF < 6%), 75 (41.2%) S1 (MRI-PDFF 6-17%), 10 (5.5%) S2 (MRI-PDFF 17.1-22%), and 20 (11%) S3 (MRI-PDFF ≥ 22.1%). Concordance of AC-5A and AC-3A with AC-5M was excellent (CCC: 0.99 and 0.96, respectively). The correlation with MRI-PDFF was almost perfect. Diagnostic accuracy of AC-5M, AC-5A, and AC3A was not significantly affected by different levels of IQR/M or SD/A. The accuracy of AC in quantifying liver fat content was not affected by reducing the number of acquisitions (from five to three), by using the mean instead of the median, or by reducing the IQR/M or SD/A to ≤5%.

Assessment of aging degradation in rubber using quasi-static components of ultrasonic longitudinal waves

Abstract Aging degradation is the main form of failure of rubber in service, leading to a decline in its physical and mechanical properties. This paper presents an efficient method for assessing the aging degradation of rubber using the quasi-static component (QSC) of ultrasonic longitudinal waves induced by acoustic radiation. The experiments quantitatively observe the response of the QSC pulse to different levels of ageing degradation. A pulse-echo ultrasonic transducer is employed to simultaneously capture the primary longitudinal wave (PLW) and QSC echoes, enabling the determination of the acoustic nonlinearity parameter of QSC with a single transducer excitation. The results suggest that, in comparison to traditional linear ultrasonic techniques based on attenuation coefficient and wave velocity measurements, the relative acoustic nonlinear parameter of QSC proves to be more sensitive to aging degradation in rubber. Particularly, the amplitude of the QSC pulse undergoes a significant change with increasing aging degradation, even when the PLW tone burst is completely attenuated. These findings confirm the effectiveness of QSC as a method for evaluating aging degradation in highly attenuative materials.

Multiparametric liver assessment in patients successfully treated for hepatitis C: a 4-year follow-up

Background Hepatitis C virus (HCV) is a major cause of chronic liver disease, in which liver stiffness increases. Liver stiffness measurements (LSM) are therefore essential in diagnosing liver diseases and predicting disease development. The study objective was to perform a comprehensive prospective assessment of the liver before, after and 4 years after treatment for HCV, including an assessment of the long-term outcome of fibrosis, steatosis and inflammation. Methods and findings Patients eligible for HCV treatment were included prospectively in 2018 (n = 47). Liver stiffness was measured using transient elastography and 2D shear-wave elastography (SWE). Blood tests, B-mode ultrasound (US) and SWE, were performed before, after (end of treatment [EOT]), 3 months after (EOT3) and 4 years after treatment (4Y). At the final visit, we added attenuation imaging and shear-wave dispersion slope (SWDS) measurements to assess steatosis and inflammation. Three months after treatment, the sustained virologic response rate was 93%. The median liver stiffness for baseline, EOT, EOT3 and 4Y was 8.1, 5.9, 5.6 and 6.3 kPa, respectively. There was a significant reduction in liver stiffness from baseline to EOT, and from EOT to EOT3. After 4 years, the mean attenuation coefficient (AC) was 0.58 dB/cm/MHz, and the mean SWDS value was 14.3 (m/s)/kHz. Conclusion The treatment for HCV was highly effective. Measurements of liver stiffness decreased significantly after treatment and remained low after 4 years. AC measurements indicated low levels of liver steatosis. Shear-wave dispersion values indicated inflammation of the liver, but the clinical implication is undetermined and should be explored in larger studies. Clinicaltrials.gov: NCT03434470 Abbreviations AC: attenuation coefficient; APRI: aspartate aminotransferase to platelet ratio index; ATI: attenuation imaging; cACLD: compensated advanced chronic liver disease; CAP: controlled attenuation parameter; FIB-4: Fibrosis-4 Index for liver fibrosis; HCC: hepatocellular carcinoma; LSM: liver stiffness measurement; NAFLD: non-alcoholic fatty liver disease; NASH: non-alcoholic steatohepatitis; SWDS: shear-wave dispersion slope; SWE: shear-wave elastography; US: ultrasound

US Markers and Necroinflammation, Steatosis, and Fibrosis in Metabolic Dysfunction-associated Steatotic Liver Disease: The iLEAD Study.

Background Attenuation coefficient (AC) and shear-wave speed (SWS) are established US markers for assessing patients with metabolic dysfunction-associated steatotic liver disease (MASLD), while shear-wave dispersion slope (DS) is not. Purpose To assess the relationship between the multiparametric US imaging markers DS, AC, and SWS and liver histopathologic necroinflammation in patients with MASLD. Materials and Methods This international multicenter prospective study enrolled consecutive patients with biopsy-proven MASLD between June 2019 and March 2023. Before biopsy, all participants underwent multiparametric US, and measurements of DS, AC, and SWS were obtained. Multivariable linear regression analyses were performed to assess the association of clinical variables and imaging markers with pathologic findings. The diagnostic performance of imaging markers for determining inflammation grade, steatosis grade, and fibrosis stage was assessed using the area under the receiver operating characteristic curve (AUC). Results A total of 124 participants (mean age, 53 years ± 15 [SD]; 62 males) were evaluated. In multivariable regression, lobular inflammation was associated with DS (regression coefficient, 0.06; P = .02), alanine aminotransferase level (regression coefficient, 0.002; P = .002), and Hispanic or Latino ethnicity (regression coefficient, -0.68; P = .047), while steatosis was associated with AC (regression coefficient, 3.66; P < .001) and fibrosis was associated with SWS (regression coefficient, 2.02; P < .001) and body mass index (regression coefficient, 0.05; P = .02). DS achieved an AUC of 0.72 (95% CI: 0.63, 0.82) for identifying participants with inflammation grade A2 or higher (moderate to severe inflammation). AC showed excellent performance for identifying participants with grade S1 (mild) or higher steatosis (AUC, 0.92 [95% CI: 0.87, 0.97]), while SWS showed excellent performance for identifying participants with fibrosis stage F2 or higher (clinically significant fibrosis) (AUC, 0.91 [95% CI: 0.86, 0.96]). Of the three US markers, SWS showed the highest AUC (0.81 [95% CI: 0.74, 0.89]) for the diagnosis of metabolic dysfunction-associated steatohepatitis. Conclusion Of the three US imaging markers (DS, AC, and SWS), DS was most associated with lobular inflammation grade at histologic examination and demonstrated fair diagnostic performance in distinguishing moderate to severe lobular inflammation. ClinicalTrials.gov Identifier: NCT04012242 Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Yin in this issue.

Calibration measurement and application of a dual-probe acoustic measurement method for seafloor sediments

The laboratory measurement of the acoustic attenuation coefficient of seafloor sediment poses a significant challenge as it is more difficult to measure with the same precision and convenience as the sound velocity. A novel dual-probe acoustic measurement method (DPAMM) addresses this challenge by simultaneously obtaining the sound velocity and acoustic attenuation coefficient of seafloor sediments, enabling stratified measurements with minimal disturbances. However, issues related to the sensitivity difference between the probes, the diameter of the sample pipe, and the inter-probe blockage can affect the accuracy of the measurement. To address these influencing factors, water was used as a reference standard for calibrating DPAMM. Experimental investigations were conducted to examine the effects of factors such as the diameter of the sample pipe, probe spacing, probe distance from the acoustic source, and probe sensitivity differences. The results revealed a positive correlation between the diameter of the sample pipe and the effective measurement distance, as well as the correction factor for probe blockage. Based on the calibration method described above, sensitivity calibration coefficients and blocking correction coefficients were derived from the experiments. The application of the stratified acoustic measurement of seafloor sediment samples demonstrates the effectiveness of the DPAMM.

Rhizophora-based particleboard bonded with soy flour and lignin as potential phantom

Rhizophora-based particleboard was evaluated for its suitability as phantom material, especially in medical physics applications. The elemental composition, effective atomic number, micrographic structures, computed tomography (CT), and attenuation properties of Rhizophora-based particleboards were examined. These investigations considered three different particle sizes and three distinct adhesive mixtures. Rhizophora sample at particle sizes of 0 to 103 µm, with 4.5% soy flour and 1.5% lignin (C6) presented with a homogenous compound with better uniformity compared with other samples, and Rhizophora sample at particle sizes of 104 to 210 µm, with 9% soy flour and 3% lignin (B12) demonstrated an effective atomic number of 8.15, which is similar to water. C6 also presented with a density distribution profile with close proximity to water. The measured attenuation coefficients of samples were aligned closely with those of water, as determined by XCOM. The results suggest that the formulation of soy flour and lignin as adhesives for Rhizophora-based particleboard is suitable for the fabricating of phantom material for medical physics applications, especially mainly due to its natural origin.

Structural, optical, luminescence spectroscopy and radiation shielding properties of Eu3+:borophosphotellurite glasses

Recently much effort is being paid to study the rare earth ions in multi component glass formers as they exhibit high enhancement in the efficiency of luminescence properties. In this direction, the present study focuses on the preparation and analysis of novel glass batches with composition of (in mol %) BPTCZEu: 40B2O3+20P2O5+15TeO2+ 10CaO+(15−x)ZnO + xEu2O3, x = 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5. The important spectroscopic techniques such as optical absorption, luminescence, excitation and decay curves are taken to analyse the BPTCZEu glasses. Luminescence spectrum of BPTCZEu comprise of emission from excited (5D0) to the lower multiplets (7FJ (J = 0−4)), among these, 5D0 → 7F2 (red luminescence) at 612 nm found to be very intense. Judd−Ofelt characteristics, Ω2, Ω4 and Ω6, were derived from different constraints. To know the site symmetry around Eu3+, the fluorescence intensity ratio of 5D0 → 7F2 vs. 5D0 → 7F1 were analysed. Exciting 7F0 → 5L6 and monitoring 5D0 → 7F2, the lifetime of 5D0 level is determined to be 2 ms which is independent of Eu3+ content. The colour coordinates for all the Eu3+ concentrations are estimated to fall in the reddish−orange region. Theoretical radiation shielding results showed that substituting Eu2O3 for ZnO in the glasses lowers photon number that can pass via the material, enhancing the glass system's trend to shield high energy radiation. These stimulated results are compared with experimental measurements of mass attenuation coefficient with respect to energy up to 662 KeV using Cs−137 source. All these findings obtained from title glasses are compared and discussed with respect to reported Eu3+:glasses and no systematic variation has been noticed either with single, bi− or multi−component glass formers and therefore needs further systematic work to relate Eu−radiation−ligand interaction.

108 m Underwater Wireless Optical Communication Using a 490 nm Blue VECSEL and an AOM.

Advanced light sources in the blue-green band are crucial for underwater wireless optical communication (UWOC) systems. Vertical-external-cavity surface-emitting lasers (VECSELs) can produce high output power and good beam quality, making them suitable for UWOC. This paper presents a 108 m distance UWOC based on a 100 mW 490 nm blue VECSEL and an acousto-optic modulator (AOM). The high-quality beam, which is near diffraction-limited, undergoes relatively small optical attenuation when using a conventional avalanche photodiode (APD) as the detector and employing 64-pulse position modulation (PPM). At the time-slot frequency of 50 MHz, the bit error rate (BER) of the UWOC was 2.7 × 10-5. This is the first reported AOM-based UWOC system with a transmission distance over 100 m. The estimated maximum transmission distance may be improved to about 180 m by fully utilizing the detection accuracy of the APD according to the measured attenuation coefficient of the blue VECSEL used. This type of UWOC system, composed of a high-beam-quality light source and a conventional detector, make it more closely suited to practical applications.

IATT liver fat quantification for steatosis grading by referring to MRI proton density fat fraction: a multicenter study.

Several preliminary reports have suggested the utility of ultrasound attenuation coefficient measurements based on B-mode ultrasound, such as iATT, for diagnosing steatotic liver disease. Nonetheless, evidence supporting such utility is lacking. This prospective study aimed to investigate whether iATT is highly concordant with magnetic resonance imaging (MRI)-based proton density fat fraction (MRI-PDFF) and could well distinguish between steatosis grades. A cohort of 846 individuals underwent both iATT and MRI-PDFF assessments. Steatosis grade was defined as grade 0 with MRI-PDFF < 5.2%, grade 1 with 5.2% MRI-PDFF < 11.3%, grade 2 with 11.3% MRI-PDFF < 17.1%, and grade 3 with MRI-PDFF of 17.1%. The reproducibility of iATT and MRI-PDFF was evaluated using the Bland-Altman analysis and intraclass correlation coefficients, whereas the diagnostic performance of each steatosis grade was examined using receiver operating characteristic analysis. The Bland-Altman analysis indicated excellent reproducibility with minimal fixed bias between iATT and MRI-PDFF. The area under the curve for distinguishing steatosis grades 1, 2, and 3 were 0.887, 0.882, and 0.867, respectively. A skin-to-capsula distance of ≥ 25mm was identified as the only significant factor causing the discrepancy. No interaction between MRI-logPDFF and MRE-LSM on iATT values was observed. Compared to MRI-PDFF, iATT showed excellent diagnostic accuracy in grading steatosis. iATT could be used as a diagnostic tool instead of MRI in clinical practice and trials. Trial registration This study was registered in the UMIN Clinical Trials Registry (UMIN000047411).

RADIATION BEHAVIOR IN BIOLOGICAL COMPOUND: EXPLORING MASS ATTENUATION AND EFFECTIVE ATOMIC NUMBERS FOR GAMMA-RAY INTERACTION

This study involved the measurement of mass attenuation coefficients (μ/ρ) for fatty acids across a range of photon energies (from 122 keV to 1330 keV). These measurements were conducted through transmission experiments employing collimated beams generated by 57Co, 133Ba, 22Na 137Cs, 54Mn, and 60Co sources, each producing beams with a diameter of 0.52 cm. The detection of attenuated radiation was achieved using a NaI (Tl) scintillation detector with an energy resolution of 8.2% at 663 keV. The obtained experimental values of (μ/ρ) were subsequently used to calculate the atomic cross-sections (σa), electronic crosssections (σe), effective atomic numbers (Zeff), and electron densities (Neff). Notably, the study revealed that (μ/ρ), σa, and σe exhibited an initial decrease with increasing photon energy, stabilizing at higher energy levels. In contrast, Zeff and Neff remained relatively constant with changing energy levels. In addition, the research acknowledged that deviations in experimental results for radiological parameters may be influenced by the physical and chemical surroundings of the substances under investigation. Encouragingly, the experimental findings were found to be consistent with values from the WinXCom database, affirming their accuracy and reliability. These outcomes contribute to a deeper understanding of the photon interaction characteristics of these biological substances across diverse energy spectra.

Investigation of the dependence of temperature attenuation of the layered bio-tissue

High-intensity focused ultrasound for solid tumor ablation is a noninvasive ultrasound hyperthermia technique wherein ultrasound is transmitted through multiple layers of biological tissues, focusing on the target area. The resulting heat accumulates in the target tissue, leading to irreversible cell death or protein necrosis, achieving tumor ablation. During treatment, the efficiency of acoustic energy converting to heat is closely related to temperature attenuation in the layered tissues. To obtain an accurate prediction of thermal damage, variations in the acoustic parameters should be measured at different temperatures. This study used two methods to induce heating to the tissues: the water heating method (WHM), which involves heat transfer from the outside to the inside, and the ultrasound heating method (UHM), wherein the heat source is located inside the tissue. The finite-amplitude insertion-substitution method was utilized to determine the attenuation coefficients of various bio-tissues such as porcine fat, muscle, and liver as the temperature increased. To mitigate the effects of viscous heating artifacts, the ‘wait then measure’ (WTM) thermometric approach was utilized using wire thermocouples to measure the temperature of the ultrasound-heated tissue. Experimental results demonstrate that the attenuation coefficient of bio-tissues varies with temperature under different heating methods. This study presents the variation in tissue attenuation using WHM at 5 MHz, while tissue categories using UHM are modeled with formulas at a frequency of 2 MHz.

Measurement of frequency-dependent shear wave attenuation coefficients using an oblique incidence pulse-echo ultrasonic method

A pulse-echo oblique incidence technique for determining the frequency-dependent attenuation of ultrasonic shear waves in metallic materials is considered and improved. To measure the attenuation coefficient, the wave signals are measured when the waveform-converted shear waves propagate over different distances. A diffraction correction is introduced to minimize the beam-spreading loss of the wave, and narrowband signals are used to minimize the effects of a downward shift in frequency. The attenuation coefficient is measured at a certain frequency, and experiments are performed over a broad bandwidth range of frequencies; a curve fitting method is then applied to these attenuation values to ensure an accurate estimate of the frequency-dependent shear wave attenuation. Experiments are performed to evaluate the effectiveness of the proposed method, and the frequency-dependent shear attenuation curves for some commonly used metallic materials are obtained. One of the most significant findings from the results is that the shear wave attenuation follows a power law dependence on frequency with exponents between 2 and 3, which lie between the theoretical values of the exponents from the classical stochastic and Rayleigh scattering theories. The effects of grain size on shear wave attenuation are investigated, and a quantitative comparison is drawn between the experimentally observed attenuation and that predicted by the classical theory. The proposed measurement method and the experimental results presented here are expected to provide good references for researchers interested in frequency-dependent shear wave attenuation behavior.

Enhancement of optical and radiation shielding properties in calcium–magnesium silicate bioactive glasses through Na2O and P2O5 additives

The present study investigates the influence of Na2O/MgO and P2O5/SiO2 substitutions on the structure and protective properties of bioactive glasses composed of 32CaO–19MgO–0.5P2O5–0.5CaF2–48SiO2 (mole %). The glass samples are prepared using the conventional melt-quenching method. Optical analyses, including refractive index (n), molar refraction (Rm), and cationic polarizability (αm), are calculated and discussed to examine structural modifications. Raman spectroscopy is employed for detailed structural analysis. The effects of compositional changes on the protective parameters are thoroughly investigated by theoretically determining mass attenuation using the newly developed Phy-X/PSD software and XCOM programs, which are then experimentally confirmed at three selected radioactive isotope energies. Experimental measurements of mass attenuation coefficient follow the sequence: MACG1 > MACG2 > MACG3 > MACG4. Raman spectroscopy results indicate that the glass network primarily consists of silicate and phosphate species as the main structural units. An increase in the molar ratio of Na2O and P2O5 improves the radiation shielding effectiveness of the samples. Among them, sample G5, with the lowest SiO2 and MgO content, exhibits the best shielding characteristics due to its high density and molar fraction of Na2O and P2O5. A correlation between microhardness and protective effectiveness is also established. The obtained results support the potential use of these glasses as dual agents for both radiation shielding and medical devices simultaneously.